CVE-2005-0400 in Linux
Summary
by MITRE
the ext2_make_empty function call in the linux kernel before 2.6.11.6 does not properly initialize memory when creating a block for a new directory entry which allows local users to obtain potentially sensitive information by reading the block.
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Analysis
by VulDB Data Team • 06/06/2019
The vulnerability described in CVE-2005-0400 represents a critical memory initialization flaw within the Linux kernel's ext2 filesystem implementation that affects versions prior to 2.6.11.6. This issue resides in the ext2_make_empty function which is responsible for creating new directory entries within the ext2 filesystem. The flaw occurs during the process of allocating and preparing memory blocks for new directory structures, where the function fails to properly initialize the allocated memory space before use.
The technical nature of this vulnerability stems from improper memory handling within the kernel's filesystem subsystem. When the ext2_make_empty function is invoked to create a new directory entry, it allocates a memory block to hold the directory structure data. However, the function does not initialize this memory block with zeros or proper default values before storing new directory entry information. This results in the block containing residual data from previous operations or memory contents that were previously allocated to other processes or kernel structures.
The operational impact of this vulnerability is significant for local users who can exploit this weakness to obtain potentially sensitive information that was previously stored in the uninitialized memory regions. When a new directory entry is created, the uninitialized memory may contain fragments of previous file data, system information, or other sensitive content that was previously stored in those memory locations. This information disclosure occurs because the kernel does not clear the memory block before writing new directory entry data, leaving remnants of prior content accessible to the local user.
This vulnerability aligns with CWE-119 which describes improper access to memory buffers and CWE-248 which addresses exposure of sensitive information through uninitialized memory. The flaw represents a classic case of information leakage through improper memory initialization, where the kernel fails to sanitize memory before reuse. From an attack perspective, this vulnerability can be categorized under the ATT&CK technique T1005 which involves data from local system repositories, and T1059 which covers command and scripting interpreter usage for exploitation.
The security implications extend beyond simple information disclosure as the leaked data could potentially contain sensitive system information, file contents, or other confidential data that might aid in further exploitation attempts. Local users can leverage this vulnerability to gain insights into the system's memory layout, potentially enabling more sophisticated attacks such as privilege escalation or targeted exploitation of other vulnerabilities. The vulnerability is particularly concerning because it operates at the kernel level and affects the fundamental filesystem operations that are critical to system security and stability.
Mitigation strategies for this vulnerability primarily involve upgrading to Linux kernel versions 2.6.11.6 or later where the memory initialization issue has been properly addressed. System administrators should implement comprehensive patch management procedures to ensure all systems are running patched kernel versions. Additionally, monitoring for suspicious filesystem operations and implementing proper access controls can help reduce the potential impact of exploitation attempts. The fix implemented in the patched versions ensures that memory blocks are properly initialized before being used for new directory entries, eliminating the information disclosure risk.